Schedule VI - Supplementary Information For Property and Casualty Insurance Underwriters (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Net Losses and Loss Adjustment Expenses Incurred Related to Current Year	$ 8,849	$ 6,784	$ 5,797
Net Losses and Loss Adjustment Expenses Incurred Related to Prior Years	(507)	(538)	(769)
Consolidated Subsidiaries
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Deferred Acquisition Costs	1,734	1,531	1,263
Reserves for Losses and Loss Adjustment Expenses	29,369	22,752	20,032
Discount, if any, deducted in Column C	68	66	61
Unearned Premiums	10,218	8,808	7,337
Net Premiums Earned	15,100	12,440	9,679
Net investment income	1,495	1,023	496
Net Losses and Loss Adjustment Expenses Incurred Related to Current Year	8,849	6,784	5,797
Net Losses and Loss Adjustment Expenses Incurred Related to Prior Years	(507)	(538)	(769)
Amortization of Deferred Acquisition Costs	2,651	2,312	1,740
Net Paid Losses and Loss Adjustment Expenses	5,073	4,093	3,141
Net Premiums Written	$ 15,732	$ 13,468	$ 11,078